diff --git a/bin/checksum_delta_diff_test.py b/bin/checksum_delta_diff_test.py
index 05cd1c3..b885889 100644
--- a/bin/checksum_delta_diff_test.py
+++ b/bin/checksum_delta_diff_test.py
@@ -1,5 +1,6 @@
 #!/usr/bin/python3
 
+#from __future__ import unicode_literals
 from scapy.all import *
 
 if __name__ == '__main__':
@@ -8,39 +9,52 @@ if __name__ == '__main__':
     e0 = Ether(src="00:00:00:00:00:00",
                dst="00:00:00:00:00:00")
 
-    e = Ether(src="02:53:55:42:45:01",
-              dst='ff:ff:ff:ff:ff:ff')
-
     i0 = IP(src = "0.0.0.0",
             dst = "0.0.0.0")
 
-    i4 = IP(src = "192.168.1.1",
-            dst = "192.168.4.2")
-
-    i6 = IPv6(src = "2001:db8:42::1",
-             dst = "2001:db8::2")
-
     t0 = TCP(dport=0, sport=0)
     #t = TCP(dport=80, sport=random.randint(49152,65535))
 
     #    print("chk_t = {}".format(t))
+
+    e = Ether(src="02:53:55:42:45:01", dst='ff:ff:ff:ff:ff:ff')
+    i4 = IP(src = "192.168.1.1", dst = "192.168.4.2")
+    i6 = IPv6(src = "2001:db8:42::1", dst = "2001:db8::2")
+    i62 = IPv6(src = "2001:db8:42::2", dst = "2001:db8::2")
     t = TCP(dport=80, sport=1337)
+    u = UDP(dport=80, sport=1337)
 
     #print("chk_t = {}".format(t))
 
     d0 = ""
     d = "A"
 
-    p.append(e / i4 / t / d)
-    p.append(e / i6 / t / d)
+    p.append(e / i4 / u / d)
+    p.append(e / i6 / u / d)
+    p.append(e / i62 / u / d)
 
     for packet in p:
         print("p = {}".format(packet.__repr__()))
         packet_rebuild = packet.__class__(str(packet))
-        chk_old = packet[TCP].chksum
-        chk_new = packet_rebuild[TCP].chksum
+        print("rebuild = {}".format(packet_rebuild.__repr__()))
+        chk_old = packet[UDP].chksum
+        chk_new = packet_rebuild[UDP].chksum
         print("chk1 = {} chk2={}".format(chk_old, chk_new))
 
+    # Get diffs -- for UDP
+    # udp_v4 =
+    # hdr.ipv4.src_addr,
+    #             hdr.ipv4.dst_addr,
+    #             8w0,
+    #             hdr.ipv4.protocol,
+    #     		    meta.length_without_ip_header,
+
+    #     			// UDP header
+    #             hdr.udp.src_port,
+    #             hdr.udp.dst_port,
+    #             hdr.udp.payload_length
+
+
 # Checksums:
 # - tcp
 # - udp
diff --git a/bin/checksum_test.py b/bin/checksum_test.py
deleted file mode 100644
index 622c4ee..0000000
--- a/bin/checksum_test.py
+++ /dev/null
@@ -1,37 +0,0 @@
-#!/usr/bin/python3
-
-from scapy.all import *
-
-if __name__ == '__main__':
-    p = []
-
-    e0 = Ether(src="00:00:00:00:00:00",
-               dst="00:00:00:00:00:00")
-
-    e = Ether(src="02:53:55:42:45:01",
-              dst='ff:ff:ff:ff:ff:ff')
-
-    i0 = IP(src = "0.0.0.0",
-            dst = "0.0.0.0")
-
-    i4 = IP(src = "192.168.1.1",
-            dst = "192.168.4.2")
-
-    i6 = IPv6(src = "2001:db8:42::1",
-             dst = "2001:db8::2")
-
-    t0 = TCP(dport=0, sport=0)
-    t = TCP(dport=80, sport=random.randint(49152,65535))
-
-    d0 = ""
-    d = "A"
-
-    p.append(e0 / i0 / t0 / d0)
-    p.append(e / i4 / t / d)
-#    p.append(e / i6 / t / d)
-
-    for test in p:
-        print("p = {}".format(test.__repr__())!)
-        packet_raw = str(test)
-        checksum_scapy = IP(packet_raw)[TCP].chksum
-        print("chk = {}".format(checksum_scapy))
diff --git a/doc/plan.org b/doc/plan.org
index a2f0fdc..b1efe5c 100644
--- a/doc/plan.org
+++ b/doc/plan.org
@@ -3198,6 +3198,18 @@ ERROR: failed to convert p.ethernet.dstAddr of type <type 'str'> to an integer
 **** TODO Explore PX
 *** TODO Integrate nat64 code into netfpga
 **** figure out how to do ANY checksums
+** Diff / Delta based checksums
+*** create test case / test theory
+**** TODO try first v6/v6
+**** using python/struct
+***** find right byte orders
+**** using python/scapy
+#+BEGIN_CENTER
+
+#+END_CENTER
+**** using p4
+
+**** using p4/netpfga
 ** NAT64/NAT46 Features in jool and tayga
 *** TODO Static 1:1 NAT46: translate from IPv4 to IPv6 with a table
 **** TODO TCP